Model railway systems have traditionally been constructed with of a set of interconnected sections of track, electric switches between different sections of the track, and other electrically operated devices, such as train engines and draw bridges. The track sections include straight, curved, and turnout sections. FIG. 1 illustrates a track section 50 for a model railway. As illustrated, the track section 50, comprising a turnout, includes a main pathway (called a mainline) and one or more diverging pathways. A point rail 60 can be repositioned with respect to the pathways to allow a train to enter a desired route. The portion of the turnout 50 which is grooved for the wheel flanges of the track is called a frog 70. The frog 70 permits the wheel flanges of cars taking one route to “pass through” the railhead of the other. The movement of the point rail 60 is driven by points 80, which, in turn, are engaged by a throwbar 90 driven by a stationary switch machine 100.
In operation, vehicle engines are energized via electricity transmitted through the electrically conductive rails of the track. The speed and direction of the vehicle is controlled by the level and polarity, respectively, of the electrical power supplied to the track rails. An operator manually pushes buttons or pulls levers to cause the switches or other electrically operated devices to function, as desired. Such model railway sets are suitable for a single operator, but unfortunately they lack the capability of adequately controlling multiple trains independently. In addition, such model railway sets are not suitable for being controlled by multiple operators.
A digital command control (DCC) system has been developed to provide additional controllability of individual vehicles and other electrical devices. A typical system includes a handheld unit (e.g., a throttle), a digital command station (DCS), and a plurality of devices each comprising an individually addressable digital decoder. The DCS is electrically connected to the train track to provide a command to a particular device (i.e., the device the operator desires to control). The DCS, in turn, may be controlled by a personal computer and/or the handheld device. The address data and the command comprise a set of encoded digital bits sent in the form of square wave packets. A suitable standard for the digital command control system is the protocol established by the National Model Railroad Association DCC Standards, the specification documents of which are hereby incorporated herein by reference. The digital command control, then, enables an operator to individually control different devices of the railway system by using decoders.
Decoders fall into two general categories: mobile decoders, which are designed to control the operations of a vehicle traveling over the railway (e.g., controlling the movement, lights, or sound of the vehicle) and accessory or stationary decoders, which control fixed equipment (e.g., switches railways turnouts, lights, signals, sound, and other immobile animation devices). One popular stationary switch machine is disclosed in U.S. Pat. No. 4,695,016 (Worack), the contents of which are hereby incorporated by reference in its entirety. This slow motion switch machine includes an output pin connected to a swing arm pivotally mounted in a housing and driven by a set of reduction gears. An electric motor drives the gears via a stall current that is low enough to allow the motor to be continuously stalled without damaging it. A printed circuit board provides electrical connections to the motor and auxiliary contacts, which can be opened and closed by a wiper mounted on the swing arm.
In railroad systems, accessory decoders are often used to provide switch routing, i.e., they are capable of operating multiple stationary switch machines in a distinct pattern that forms a route through the switches by issuing one control command. Conventional accessory decoders provide switch routing by locating multiple decoders on a single printed wiring board. This allows a common control to organize routing among the controlled outputs. This approach, however, is limited by the maximum number of outputs that can be located on the wiring board, and by the need to run wiring from the controller to each switch motor. In addition, conventional decoders suffer from other disadvantages. For example, if the train approaches a track section having a misaligned switch (i.e., a switch aligned opposite with respect to the travel direction of the train), a short circuit can result, stopping the train until the switch is correctly aligned. Furthermore, existing accessory decoders only place the stationary switch machine in the position it held at the time of the last power off cycle. Consequently, if a user forgets the last position of the switch, the train may unexpectedly veer off course, causing an accident.
Consequently, there exists a need to provide an accessory decoder that provides a stationary switch machine with multiple switch addresses, senses switch misalignment and repositions the switch correctly, and/or also allows the operator, at his/her option, to control multiple command variables to alter the functionality of the switch.